Backrest for a seating structure with an adjustable sacral support

ABSTRACT

A backrest includes a back member having an upper and lower region and a frame member. A sacral support member has at least one end connected to one of the frame member and the back member and an opposite free end. The sacral support member supports the back member at the lower region thereof. A fulcrum member is moveably disposed between a portion of the sacral support member and one of the frame member and the back member. The fulcrum member is moveable toward and away from the free end of the sacral support member. A method for adjusting a backrest includes engaging a lower region of a back member with a sacral support member having a free end and a cantilevered length, engaging the sacral support member with a fulcrum member, and moving the fulcrum member toward and away from the free end of the sacral support member so as to thereby shorten and length the cantilevered length of the sacral support member.

[0001] This application claims the benefit of U.S. ProvisionalApplication Serial No. 60/418,483, filed Oct. 15, 2002, the entiredisclosure of which is hereby incorporated herein by reference.

BACKGROUND

[0002] The present invention relates generally to a backrest for aseating structure, and in particular, to a backrest having an adjustablesacral support.

[0003] The spine is broken down into four general regions: cervical(neck), thoracic (upper back), lumbar (lower back) and sacral/pelvic(tail bone). In some circumstances, back problems can be experienced atthe point were the lumbar spine connects to the sacrum. In particular,sitting up straight can be difficult for the users of many chairs. Forexample, in many seating devices, a void exists between the backrest ofthe chair and sacrum of the user. As a result, the user will be placedin a position of poor posture, lack of muscle control and discomfort.Slouching can lead to a number of problems, including increased fatigueand fidgeting due to discomfort. In addition, slouching may also lead toincreased pressure on the lumbar discs or muscle spasms. Long-termproblems such as lower back pain, sore necks and the like can alsooccur.

[0004] In order to alleviate some of these problems, previous attemptshave been made to provide better support for the sacrum. Some of thesedevices, however, as disclosed for example in U.S. Pat. No. 5,577,811,are not readily adjustable to suit the individual needs of the user.Others, while adjustable, are relatively complex and expensive tomanufacture. Accordingly, a need remains for an improved, simplesacral/pelvic support that is readily adjustable.

SUMMARY

[0005] The present inventions are defined by the claims, and nothing inthis section should be read as a limitation on those claims. Rather, byway of general introduction and briefly stated, various preferredembodiments are described that relate to a seating structure having abackrest with an adjustable sacral support.

[0006] In one preferred embodiment, a back member has an upper and lowerregion and a frame member. A sacral support member has at least one endconnected to one of the frame member and the back member and an oppositefree end. The sacral support member supports the back member at thelower region thereof. A fulcrum member is moveably disposed between aportion of the sacral support member and one of the frame member and theback member. The fulcrum member is moveable toward and away from thefree end of the sacral support member.

[0007] In one preferred embodiment, the sacral support has a portionsupported by a lumbar support member, which supports the back memberabove the sacral support.

[0008] In another aspect, a method for adjusting a backrest includesengaging a lower region of a back member with a sacral support memberhaving a free end and a cantilevered length, engaging the sacral supportmember with a fulcrum member, and moving the fulcrum member toward andaway from the free end of the sacral support member so as to therebyshorten and length the cantilevered length of the sacral support member.

[0009] The various preferred embodiments provide significant advantagesover other seating structure having sacral supports. In particular, thesacral support can be easily and quickly adjusted simply by moving thefulcrum member to the desired position. The relatively few andinexpensive parts provide improved support for the user's sacrum in asimple and efficient manner.

[0010] The present invention, together with further objects andadvantages, will be best understood by reference to the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a perspective view of one embodiment of a chair having abackrest.

[0012]FIG. 2 is an exploded perspective view of a backrest assembly.

[0013]FIG. 3 is a side view of a back support member.

[0014]FIG. 4 is a cross-sectional view of the back support member takenalong line 4-4 of FIG. 3.

[0015]FIG. 5 is a front view of a back support member.

[0016]FIG. 6 is a cross-sectional view of the back support member takenalong line 6-6 of FIG. 5.

[0017]FIG. 7 is a side view of a back support fulcrum member.

[0018]FIG. 8 is a partial top view of the back support fulcrum membershown in FIG. 7.

[0019]FIG. 9 is front view of a back member with a cut-out therein.

[0020]FIG. 10 is a front view of the back member shown in FIG. 9 with ahinge portion overmolded thereon.

[0021]FIG. 11 is a partial cross-sectional view of the back member takenalong line 11-11 of FIG. 10.

[0022]FIG. 12 is a rear perspective view of one embodiment of abackrest.

[0023]FIG. 13 is a cross-sectional view of the backrest spine.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0024] The terms “longitudinal” and “lateral” as used herein areintended to indicate the direction of the chair from front to back andfrom side to side, respectively. Similarly, the terms “front”, “side”,“back”, “forwardly”, “rearwardly”, “upwardly” and “downwardly” as usedherein are intended to indicate the various directions and portions ofthe chair as normally understood when viewed from the perspective of auser sitting in the chair.

[0025] Referring to the drawings, FIG. 1 shows one embodiment of a chairhaving tilt control housing 10, seat 200, back support 304 and back 302.It should be understood that the term “housing” generally refers to anysupport member that supports another member, and includes, but is notlimited to a structure that provides an enclosure. A pair of armrests400 extends from, move with and define a portion of the back support304. Preferably, the back support 304 is pivotally mounted to thecontrol housing 10, and the seat 200 is pivotally mounted to the backsupport 304 via a pivot axis located on the armrests 400 at theapproximate hip joint of the user above the seating surface. The seat200 is further slideably and pivotally supported by the tilt controlhousing.

[0026] It should be understood that the terms “mounted,” “connected”,“coupled,” “supported by,” and variations thereof, refer to two or moremembers or components that are joined, engaged or abutted, whetherdirectly or indirectly, for example, by way of another component ormember, and further that the two or more members, or interveningmember(s) can be joined by being integrally formed, or by way of variousfastening devices, including for example and without limitation,mechanical fasteners, adhesives, welding, press fit, bent-over tabmembers, etc.

[0027] In operation, the housing 10, seat 200 and back support 304, withthe armrests 400, form a three-bar linkage with a slide. It should beunderstood that the term “slide,” as used herein, refers to two membersthat translate relative to each other, whether by direct sliding or byrolling. Preferably, the pivot axis formed between the seat 200 andhousing 10 is positioned forwardly of the pivot axis formed between theback support 304 and housing 10, which axis is positioned forwardly ofthe pivot axis formed between the back support 304 and the seat 200,such that the backrest 300 and back support 304 tilt rearwardly at agreater rate and angle than does the seat 200. Preferably, the backtilts relative to the seat at about a preferred 2:1 ratio, such that theshirt-tail pull effect is avoided. Of course, other synchrotilt ratiosare contemplated and suitable. In addition, the configuration of theback support, the seat and the various positions of the pivot axes,allow the seat to pivot about the ankles of a user seated in the chair,preferably without the front edge of the seat rising as the user tiltsrearwardly. The three-bar linkage provides a simple and compactmechanism that avoids the use of additional links. Additionally, byforming the linkage assembly from the seat, back support and housing,complex and expensive links and load bearing parts are avoided.

[0028] Referring to FIG. 1, a base 26, preferably a five arm base withcasters, is mounted to the bottom of a support column 12, which supportsthe housing, in a conventional manner, although one of skill in the artwould understand that other support columns and bases can be used tosupport the housing, including fixed height support columns andnon-rolling bases, including for example a base configured with glides.

[0029] Referring to FIGS. 1, 2 and 12, one embodiment of a backrest 300includes a backrest frame member, or back support member 304, and a backmember 302. The support member 304, otherwise referred to as a framemember, includes a lower support member 308 having a pair of forwardlyextending arms 310 that are pivotally connected to the tilt controlhousing 10.

[0030] As shown in FIGS. 2 and 12, a rear portion of the lower supportmember forms an upwardly extending arm 322. An upper support member 324,or spine, has a lower end 326 that mates with and is secured to the arm322 with a pair of fasteners 327. A cover can be disposed over thefasteners to provide a smooth, aesthetic appearance. By making thesupport member 304 in two-pieces 308, 324 the backrest can bedisassembled and the chair can be shipped in a smaller package. Inparticular, the arm 322 of the lower backrest support preferably doesnot extend upwardly above the uppermost surface of the armrests, suchthat the base, seat and armrests can be compressed to a relatively shortheight. In turn, the backrest 300 can be easily assembled by the enduser with a pair of fasteners. Moreover, the backrest can be madeoffline, if desired. As shown in FIG. 2, the lower end 326 of the spineflares outwardly and defines a pair of opposite landings 328 that matewith the back member 302.

[0031] The spine 324 extends upwardly and has a pair of arms 330 thatextend upwardly and outwardly from an upper end thereof. The ends of thearms each have a pad 332 that is secured to the back member 302 with afastener. In particular, as shown in FIG. 2, a boss 303 extends from therear of the back member and supports the pad and receives the fastener.A front surface of the spine has a rack, or a plurality of notchesformed thereon. In one embodiment, the rack is formed on a lumbarsupport insert 820, which is secured to the front side of the spine witha plurality of fasteners 822. The lumbar support insert 820 and spinecan be made of various materials, such as Capron 8233G-33% Glass FilledNylon 6, or other materials such as aluminum, steel, fiberglass,composites, plastic, or some other rigid but resilient material.

[0032] Referring to FIGS. 2 and 13, in one preferred embodiment, thespine 324 has a plurality of forwardly extending fins 821, while thelumbar support insert 820 has a plurality of rearwardly extending fins823 that are shaped to be inserted or nested in the spaces formedbetween the plurality of fins 821. In this way, the spine and insert arevery strong and resistant to bending, yet provide substantiallytorsional flexibility. In addition, the two pieces can be easily madefrom molded plastic, with thinner walls and less material. In addition,the insert 820 and spine 824 can be spaced apart along the sides thereofto form a gap.

[0033] Referring to FIGS. 2, 9 and 10, the back member 302 is preferablymade of a resilient, compliant material, including various polymeric orplastic materials. For example, in one preferred embodiment, the backmember is molded of a polypropylene 76523 Montel Profax material. Theback member 302 has a top 336, a bottom 338 and opposite, curvilinearsides 340. The sides 340 preferably have a concave, or hour-glass shape.The top 336 of the back member is preferably curved and has a convexfront, body-supporting surface 342 along a peripheral portion thereof.

[0034] The back member has a lumbar region 344, a thoracic region 346and a lower sacral region 348. The lower region includes a cut-out 350shaped to be received on the lower end 326 of the spine, with a pair ofbosses 352 positioned to mate with holes formed in the landings 328. Inone embodiment, the lower region has a sacral regions that is formed bya forwardly extending portion at the center of the lower region. A pairof fasteners secure the bottom of the back member 302 to the landings328. The back member 302 has a plurality of openings 354 formedtherethrough. Preferably, an array of openings in the lumbar region 344are elongated in the longitudinal direction, which runs between the topand the bottom of the back member. The openings 354 are preferablystaggered. For example, in one preferred embodiment, adjacent verticalcolumns of openings are offset in the vertical direction, such that theopenings in adjacent columns are not horizontally aligned.

[0035] As with the lumbar region 344, the thoracic region 346 alsoincludes an array of staggered elongated openings 354. Preferably, theelongated openings formed in the thoracic region are not as elongated,on average, as the openings in the lumbar region. This means, of course,that an occasional opening, or plurality of openings, in the thoracicregion can have a greater elongation than an opening or plurality ofopenings in the lumbar region.

[0036] Likewise, the lower region 348 has an array of staggeredelongated openings 354 formed therein, again, with an average elongationless than that of the lumbar region. Referring to FIGS. 2 and 9-10, inone embodiment, the elongated openings 355 in the lower regiontransition from a longitudinal orientation to a lateral orientation,with the transition being made progressively lower as it moves from acenter line outboard, so as to form a generally triangular region oflateral openings. Some of the openings are curved to make thetransition.

[0037] The elongated openings in the lumbar region and the adjacenttransition areas of the thoracic and lower regions are preferablyobround 356. The shapes of the openings then transition from the obroundshape to a peanut-shaped opening 358 as the location thereof movesupwardly, and then eventually the peanut-shaped openings are closed at amiddle thereof to form substantially circular openings 360 adjacent thetop and bottom of the back member. In addition, smaller circularopenings 362 are formed along the opposite sides of the back member,including at the lumbar region, and around the entire peripheral portionof the back member. In the embodiment of FIG. 2, the openings in thelower region do not transition to a peanut shape, but rather preferablystay obround, with an outer perimeter of circular openings 362. Ofcourse, it should be understood that the opening could so transition inthe lower region, and can remain in a substantially verticalorientation, as shown for example in FIGS. 1 and 12.

[0038] The back member 302, especially in the lumbar region, alsopreferably has a first thickness along the center line 364 thereof, anda second thickness at the peripheral sides 366 thereof, with the secondthickness being greater than the first thickness. For example, in thelumbar region, one preferred first thickness is about 2 mm, and onepreferred second thickness is about 3 mm. As shown in FIG. 2, the backmember is preferably bowed forwardly at the lumbar region 344. The edgeof the back member preferably is formed as a bead. The back member ispreferably formed by molding.

[0039] Referring to FIGS. 2-11, a second back support configurationincludes a first support member 1300 and a second support member 1302.In one preferred embodiment, the first support member 1300 is formed asa loop having a base 1304, a pair of arms 1306 and a support band 1308or belt extending between the two arms 1306. The support band has aforwardly facing surface 1310 that engages and supports a rear surfaceof the back member 302. A downwardly opening recess 1312 or pocket isformed in the middle portion of the belt, as best shown in FIGS. 5 and6. The recess 1312 forms a guide or track for a portion of the secondsupport member 1302.

[0040] As best shown in FIGS. 3 and 4, the second support member 1302has a J-shape, with a base arm 1314 connected to a support arm 1316having an end 1318, which is shaped and configured to be received in therecess 1312 of the second support member. The bottom of the J-shapedsupport member 1302, or a curved portion 1328 forms a free end of thesupport member 1302. The end 1318 of the support arm is supported by thelumbar support 1300 as it slides vertically in the recess, so as toallow the first and second support members to function independently. Atthe same time, the loop supports the support arm 1316 laterally and inthe fore/aft direction. Alternatively, the end 1318 of the support arm1316 can remain unsupported, or it can be fixedly connected to the firstsupport member, or lumbar support, or to the frame.

[0041] The base arm 1314 has an upper end 1320 disposed between the baseof the first support member and the lumbar insert member. A fastenersecures the first support member 1300 and the second support member 1302to the insert member 820. The arms 1314, 1316 of the second supportmember, once installed, function as a cantilevered spring, which issupported at ends 1302 and 1318 and has free end 1328. The base arm 1314has a plurality of longitudinally extending and rearwardly facinggrooves 1322, 1324, which define a plurality of ridges. The base arm1314 also has a step 1326 formed at the bottom thereof, which isconnected to the curved portion 1328 that transitions to the support arm1316 and provides additional flexibility between the arms 1314 and 1316.In this way, the overall support member 1302, including both arms actingin concert, functions as a cantilevered spring, while the individualarms 1314, 1316 act as individual springs that provide additionalindependent flexibility.

[0042] Referring to FIGS. 2, 7 and 8, a fulcrum member 1330 is disposedbetween the insert member 820 and the base arm 1314 of the secondsupport member. The fulcrum member includes a base portion 1344 forminga cavity 1348 that substantially surrounds and conforms to the forwardsurface of the insert member 820. The base portion includes a pluralityof hook members 824 that engage and slide along the sides 826 of thelumbar insert support member 820. Preferably, the hook members extendthrough the gap 829 formed between the spine and the insert member. Inone embodiment, the fulcrum member further includes a detent or latchmember that engages the rack to releasably secure the fulcrum member ina plurality of vertical positions. Alternatively, or in combination, thefulcrum includes a guide member 1332 or ridge formed in the cavity 1348that rides in a groove 1334 formed in the spine insert member. In oneembodiment, the fulcrum member includes a pair of handles 1336. Thehandles extend outwardly and downwardly and include a grippable portion1338, formed form example as a plurality of annular ridges, on the endsthereof. The front portion of the fulcrum member include a pair of guidemembers 1340 or tabs that ride in the outer channels 1322 formed in thebase support arm. The fulcrum, first support member and second supportmember are preferably made of one or more types of plastic, such asnylon or glass-filled nylon, but can be made of other materials, such asmetal, wood, composites, fiberglass and the like.

[0043] It should be understood that in an alternative embodiment, one orall of the sacral support member, the lumbar support member and thefulcrum member can be connected to the back member and engage the frame.

[0044] In operation, the user grips one or both of the fulcrum handles1336 and moves the fulcrum in the vertical direction to a desiredposition. As the fulcrum is lowered, it shortens the cantilevered lengthof the support member 1302, i.e., the distance between the fulcrum andthe bottom curved portion 1328, and the arms 1314, 1316 in particular,and provides a firmer, more rigid support for the lower region 348 ofthe back member as it engages the rear surface thereof. The user canraise the fulcrum 1330 so as to provide a greater cantilevered length,which in turn provides more flexibility of the support member and acorresponding less rigid support of the back member in the lower region.

[0045] Referring to FIGS. 9-11, the back member 302 can be modified toimprove the flexibility of the lower region thereof. In particular, aU-shaped cut-out 1350 can be made in the lower region, for example alongone row of openings 354 as they transition from the vertical to thehorizontal. In this way, the lower region 348 is provided with a centralflap 1352 or support region at the sacral region of the user's back,which is spaced from a firmer lower portion 1356. The back member isthen inserted into a mold, wherein a hinge portion 1354 is overmolded onthe back member over the cut-out so as to flexibly connect the flap 1352with the lower portion 1356 of the back member. In one embodiment, thehinge 1354 is formed as a living hinge, with a bellows shape. Of course,it should be understood that the hinge can be in-molded in the originalback member, which thereby avoids the cutting and overmoldingoperations. In addition, it should be understood that the back membercan be provided with greater flexibility by providing a thinner materialin certain regions, or by providing other hinge type devices, notlimited to a living hinge or molded hinges. In this way, the flapportion 1352 of the lower region 348 of the back member being acted uponby the support arm 1316 of the first support member is provided withgreater flexibility to move in response to the position of the supportmember 1302 as the fulcrum member is moved to a desired position. In oneembodiment, the hinge is formed from an elastomeric material, such as athermoplastic elastomer.

[0046] The configuration of the spine 324 and back member 302 providesmany advantages. For example, the compliant back member 302, with itslarger, or longer, openings in the lumbar region, and its lesserthickness along the center portion, allow that region to be moreflexible, such that it can be formed and supported by the lumbar supportand/or sacral support. In addition, the entire back is allowed toconform to the back of the user, and in particular at the edge portionsthereof, and can flex about the center spine in torsion, which is mademore flexible by way of the two-piece construction with nested fins, andalso about the bowed lumbar region. In essence, the intelligence of thebackrest is shared by the spine 324 and the back member 302. In thisway, the backrest provides greater comfort than a backrest formed with aperipheral, and relatively stiff or non-compliant, frame. In addition,by securing the back member 302 to the arms of the spine at a locationspaced below the top of the back 336, including at about 14 inches inone embodiment, and preferably between about 2 inches and about 12inches, and more preferably between about 4 inches and about 8 inches,the top peripheral portion can flex in response to movement from theuser's shoulder and neck and further avoids a “hammock” effect betweenthe top and bottom of the backrest.

[0047] In addition, the spine member is in essence modular, or providesa mounting configuration, which allows the manufacturer to installvarious support configurations on the same spine. In this way, forexample, different back supports can be configured to mount on the samespine to provide an adjustable lumbar support, or a lumbar support withan adjustable sacral support. Of course, other adjustment configurationswould be suitable.

[0048] Although the present invention has been described with referenceto preferred embodiments, those skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. As such, it is intended that the foregoingdetailed description be regarded as illustrative rather than limitingand that it is the appended claims, including all equivalents thereof,which are intended to define the scope of the invention.

What is claimed is:
 1. An backrest comprising: a back member having anupper and lower region; a frame member; a sacral support member havingat least one end connected to one of the frame member and the backmember and an opposite free end, wherein said sacral support membersupports the back member at said lower region thereof; a fulcrum membermoveably disposed between a portion of said sacral support member andone of said frame member and said back member, wherein said fulcrummember is moveable toward and away from said free end of said sacralsupport member.
 2. The backrest of claim 1 wherein said at least one endof said sacral support member is connected to said frame member andwherein said fulcrum member is moveably disposed between said portion ofsaid sacral support member and said frame member.
 3. The backrest ofclaim 2 wherein said sacral support member comprises a first supportmember flexibly connected to a second support member at said free end ofsaid sacral support member.
 4. The backrest of claim 3 wherein saidfirst support member is fixedly connected to said frame member andwherein said fulcrum member is moveably mounted on said frame member andengages said first support member.
 5. The backrest of claim 4 whereinsaid second support member has an end opposite said free end supportedby a lumbar support member.
 6. The backrest of claim 5 wherein said endof said second support member is slidably supported by said lumbarsupport member.
 7. The backrest of claim 5 wherein said lumbar supportmember supports said backrest above said sacral support.
 8. The backrestof claim 1 wherein at least a center portion of said lower region ofsaid back member is flexible, wherein said sacral support membersupports said back member at said center portion of said lower region.9. An backrest comprising: a back member having a lower region and alumbar region positioned above said lower region; a frame member; alumbar support member connected to said back member and supporting saidback member at said lumbar region; a sacral support member having atleast one end connected to the frame member and an opposite free end,wherein said sacral support member supports the back member at saidlower region thereof; a fulcrum member moveably disposed between aportion of said sacral support member and said frame member, whereinsaid fulcrum member is moveable toward and away from said free end ofsaid sacral support member.
 10. The backrest of claim 9 wherein saidsacral support member comprises a first support member flexiblyconnected to a second support member at said free end of said sacralsupport member, and wherein said first support member is connected tosaid frame and said second support member is coupled to said lumbarsupport.
 11. The backrest of claim 10 wherein said second support memberis slidably supported by said lumbar support member.
 12. A method foradjusting a backrest comprising: engaging a lower region of a backmember with a sacral support member having a free end and a cantileveredlength; engaging said sacral support member with a fulcrum member; andmoving said fulcrum member toward and away from said free end of saidsacral support member so as to thereby shorten and length saidcantilevered length of said sacral support member.
 13. The method ofclaim 12 wherein said sacral support member is connected to a framemember, and wherein said fulcrum member is moveably connected to saidframe member.
 14. The method of claim 12 wherein said sacral supportmember comprises a first support member flexibly connected to a secondsupport member at said free end of said sacral support member.
 15. Themethod of claim 14 wherein said first support member comprises an endopposite said free end fixedly connected to said frame and said secondsupport member comprises an end opposite said free end supported by alumbar support member.
 16. The method of claim 15 wherein said end ofsaid second support member is slidably supported by said lumbar support.17. The method of claim 15 wherein said lumbar support supports saidbackrest above said sacral support.